For recording of arbitrary information in the form of a visible image, paper has been used conventionally. Also, for recording of arbitrary information on paper, a developer such as an ink has been used. In recent years, there has been research on a display device which displays such arbitrary information in the form of image data, such as a liquid crystal display device, which can be handled easily in the same manner as paper.
Meanwhile, as an image forming apparatus for outputting information as a visible image on a sheet of paper, a laser printer has been widely used along with analog and digital copying machines.
These recording apparatuses form an image by the method in which an electrostatic charge image formed on a photoreceptor is developed using developer particles such as toner and then the developed image is transferred onto a sheet of paper. Meanwhile, printing devices which directly form an image on a sheet of paper have also been widely used. For example, ink-jet printers and thermal printers represent such printing devices. More recently, for example, Published Japanese Translations of PCT International Publication for Patent Applications No. 503221/1989 (Tokuhyohei 1-503221) proposes an image forming apparatus in which an image is directly formed on a recording medium by charged particles which are flown by an electrical force generated by application of an electric field to the charged particles, and are adhered onto a recording medium by changing a potential applied to a control electrode having a plurality of passage pores which are provided in the flying path of the charged particles.
Japanese Unexamined Patent Publication No. 257133/1993 (Tokukaihei 5-257133) proposes a recording method in which an image is recorded by forming an electrostatic charge image on a recording medium having photosensitivity. Also, Japanese Unexamined Patent Publication No. 67141/1994 (Tokukaihei 6-67141) proposes a method in which an image is formed on a recording medium which is in the form of a sheet.
However, the above conventional arrangements have the following problems.
As described, in the above examples, the main recording medium for an arbitrary visible image is paper. Paper is inexpensive and can be easily processed in arbitrary shapes and allows information to be recorded as a visible image conveniently. Further, because a single sheet of paper is thin and light, paper is very easy to handle.
However, while image information formed on paper can be erased or corrected to some extent by various methods, it cannot be erased or corrected completely.
Further, when recording some image information on a sheet of paper, it is absolutely required to use a developer such as toner and ink to visualize the image information. Also, while a single sheet of paper may be light, it adds up to a substantial weight as the amount of information to be recorded is increased.
Faced with and in order to solve these drawbacks, research has been active on a display device which displays arbitrary visual information in the form of electrical image data, such as well-known liquid crystal displays, which are small and light-weight and therefore are easy to carry. Such devices are advantageous because they are capable of storing a large amount of information in a memory and, unlike paper, do not result in an increase in weight even when the amount of information is increased. However, these devices require an energy source such as battery and are quite expensive at present. Further, these devices have a drawback that the degree of freedom in terms of data manipulation is poor as they require other devices such as a keyboard in order to allow user to manipulate data, such as addition and deletion of data.
Meanwhile, as mentioned above, a laser printer, along with analog and digital printers, has been widely used as an image forming apparatus for outputting information as a visible image on a sheet of paper. This recording apparatus forms an image by the method in which an electrostatic charge image formed on a photoreceptor is developed using developer particles such as toner and the developed image is transferred onto a sheet of paper. Meanwhile, printing devices which directly form an image on a sheet of paper have also been widely used. For example, ink-jet printers and thermal printers represent such printing devices. More recently, there is proposed an image forming apparatus in which an image is directly formed on a recording medium by directly adhering toner to the recording medium.
These devices also require a developer for recording the image on a sheet of paper, and it is difficult to correct or erase the image formed on the sheet by these devices other than by forming another image on the original image. Thus, once the image is formed by these devices, it is practically impossible to reuse the sheet bearing the image. Further, these devices are quite complex and expensive.
Japanese Unexamined Patent Publication No. 257133/1993 (Tokukaihei 5-257133) and No. 18917/1994 (Tokukaihei 6-18917) disclose a method in which an image is formed by charges of an electrostatic charge image which is formed on a recording medium having photosensitivity using an electrophotographic process. This method requires the recording medium to be photosensitive and this limits the selection of materials to be used as the recording medium, setting a limit to the cost of the material that can be reduced. Thus, this method is not preferable.
Also, in the arrangement of the device as disclosed in Japanese Unexamined Patent Publication No. 5418/1995 (Tokukaihei 7-5418), because multi-stylus is used, the driver for driving a high voltage applied to each needle electrode needs to have significantly high voltage resistance, and this inevitably increases the number of components, size, and cost of the device, and lowers reliability of the device.
Further, Japanese Unexamined Patent Publication No. 67141/1994 (Tokukaihei 6-67141) proposes an image forming apparatus which forms an image on a recording medium made of a liquid crystal material. However, this apparatus requires the material of the recording medium to have heat resistance due to the fact that fixing means and a transfer voltage are not controlled when carrying out printing on the recording medium. This sets a limit to the selection of the material, and the cost associated with the material is inevitably increased. This apparatus also has a problem that sufficient image formation is prevented as the image is disturbed by a strong electric field used in transfer.